In aerospace design it is desirable to seal any gaps between components of flight surfaces to present a smooth surface to the passing airflow. This reduces losses and prevents undesirable fluid flow effects such as separation of the boundary layer and subsequent loss of lift.
Components of aircraft flight surfaces such as wings, tail planes, fins, landing gear doors and control surfaces (e.g. flaps, slats, rudders, ailerons and spoliers) tend to move in use both intentionally in response to a control input (in the case of control surfaces) and unintentionally due to thermal expansion and contraction and stresses experienced in use.
As such, the width of the gaps to be sealed between components varies depending on the relative position of the components. Known seal technology utilises resilient seals which are mounted to a first component to seal against a second adjacent component and resiliently deform to the seal gap as it varies.
Such gap width variation is observed between variable camber flaps at the trailing edge of aircraft wings. The gap width between the wing and the flap not only changes due to control input, but also changes as the wing and flap thermally expand and contract with variations in operating temperature and during the flight cycle during which a range of stresses are experienced.
Furthermore, the gap width can vary along the length of the gap itself (i.e. along the wing span).
Traditionally, such gaps are sealed with the use of unitary flexible seals mounted to a first component and abutting a second component to seal against it and thereby seal the gap. These seals need to be sufficiently flexible and resilient to maintain the sealing effect during changes in the gap width but stiff enough to prevent significant deformation under the action of the air passing over the flight surface in flight.
A problem with such seals is that the requirements of flexibility to account for changes in gap width and stiffness to prevent deformation under fluid loading are counteractive. As such, it is difficult to design a seal that will fulfill both requirements.
Furthermore, variations in seal gap along the wing span are difficult to seal effectively as unitary seals are often too laterally stiff to account for these changes.
Also, seals are common in which the second component slides over a seal surface. As such there needs to be a seal flange of significant width (at least as wide as the maximum gap width) which inherently decreases the structural stiffness of the seal.
It is an aim of the present invention to overcome or at least mitigate one or more of the above problems.